1. Field of the Invention
The present invention relates to a color filtering device and a display apparatus using the same. More particularly, the present invention relates to a color filtering device having both color filtering function and polarization conversion function and a projection apparatus using the same.
2. Description of Related Art
FIG. 1A is a schematic structural view of a conventional projection apparatus. Referring to FIG. 1A, a conventional projection apparatus 100 includes an illumination system 110, a liquid crystal on silicon panel (LCOS panel) 120, and an imaging system 130. The illumination system 110 includes a lamp module 112, a light integration rod 114, a color wheel 116 and a polarization conversion system (PCS) 118. The lamp module 112 emits an illumination beam 113. The illumination beam 113 passes through the light integration rod 114, the color wheel 116, the PCS 118 in sequence and travels to the LCOS panel 120. The LCOS panel 120 converts the illumination beam 113 into an image beam 113′ and makes it project to the imaging system 130. The imaging system 130 includes a plurality of lenses 132, and the imaging system 130 projects the image beam 113′ onto a screen (not shown).
FIG. 1B shows spots formed by the illumination beam projected onto the PCS and a cross-section of the PCS in FIG. 1A from top to bottom. Referring to FIGS. 1A and 1B, the PCS 118 has a light incident surface 118a and a light emitting surface 118b. The light incident surface 118a has a plurality of transparent regions 119a and a plurality of light shielding regions 119b which are alternately arranged. Since light rays incident on different positions of the light integration rod 114 with different angles are reflected different times in the light integration rod 114, the illumination beam 113 projects a plurality of spots 113a at different positions on the light incident surface 118a of the PCS 118. Additionally, since the positions of the spots 113a on the light incident surface 118a is related to the angles and positions of the light rays incident on the light integration rod 114, the spots 113a are not arranged at equal intervals.
However, as the widths of the transparent regions 119a and the light shielding regions 119b of the PCS 118 are generally the same, parts of the spots 113a fall in the light shielding regions 119b and cannot be utilized by the projection apparatus 100 to project the display image, thus resulting in a loss of brightness of the display image approaching 15-20%. Furthermore, as a position tolerance of a lampwick 112a of the lamp module 112 is generated during manufacturing or assembly, the spots 113a cannot be accurately focused on the transparent regions 119a, and parts of the spots 113a fall on the light shielding regions 119b, which results in a loss of brightness of the display image.
Referring to FIGS. 1A and 1C, symbol 113b in FIG. 1C represents spots formed by the illumination beam 113 projected on the color wheel 116. As the color wheel 116 is composed of a plurality of filtering parts 116a with different colors, and in a period from Time T1 at which a juncture 116b of two neighboring filtering parts 116a passes by the left end of a horizontal line 113b′ of the spot 113b to Time T2 at which the juncture 116b passes by the right end of the horizontal line 113b′, the horizontal line 113b′ falls on the filtering parts 116a with two different colors at the same time, light with two different colors are generated. Accordingly, in the period from Time T1 to Time T2, the LCOS panel 120 does not perform image processing, which results in the decrease of brightness of the display image. Referring to FIG. 1D, similarly, the same problem also occurs in a period from Time T3 at which the juncture 116b passes by the right end of a horizontal line 113b″ of the spot 113b to Time T4 at which the juncture 116b passes by the left end of the horizontal line 113b″. 
Another conventional projection apparatus uses two fly eyes to replace the above light integration rod 114 to provide a light uniform function. However, an alignment tolerance is generated when the two fly eyes is assembled, so the spots formed by the illumination beam imaged on the PCS cannot be accurately focused on the transparent regions after the illumination light passes through the fly eyes, which also results in the loss of brightness of the display image.